login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A261174 Number of multigraphs on 4 unlabeled nodes with n edges where the edges can be of two colors. 0

%I

%S 1,2,9,30,90,248,650,1560,3560,7680,15786,31076,58905,107768,191180,

%T 329664,554038,909558,1461655,2302950,3563482,5422392,8124040,

%U 11997648,17482295,25156872

%N Number of multigraphs on 4 unlabeled nodes with n edges where the edges can be of two colors.

%t Needs["Combinatorica`"];n = 4; nn = 25; CoefficientList[Series[PairGroupIndex[SymmetricGroup[n], s] /.Table[s[i] -> 1/(1 - x^i)^2, {i, 1, Binomial[n, 2]}], {x, 0, nn}], x]

%Y Cf. A050531.

%K nonn

%O 0,2

%A _Geoffrey Critzer_, Aug 10 2015

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 27 03:21 EDT 2020. Contains 337380 sequences. (Running on oeis4.)